This small, dark brown saprobe appears in northern and montane areas of North America, and can be recognized quickly if a drop of KOH or ammonia is applied to its cap, producing a green color change. But without the chemical test . . . well, you're looking at a little brown mushroom with a white spore print and no distinctive odor or taste. In short, you may need to unpack your microscope.

Collybia alkalivirens is a synonym.

Description:

Ecology: Saprobic; growing alone, scattered, gregariously, or in clusters on soil, leaf and needle litter, woody debris, and among mosses or ferns; found in hardwood, conifer, and mixed forests; summer and fall; apparently widely distributed in northern North America, the Appalachians, and the Rocky Mountains.